The present invention relates to disc harrows and has particular reference to a tandem disc harrow having front and rear pairs of disc gangs and of the type including a frame structure, together with a bell crank lever arrangement embodying a pivot shaft, trailing wheel axle arms, and a crank arm which, when swung in a fore and aft direction, causes the frame structure to become either raised or lowered, depending upon the direction of swinging movement. Still more particularly, the invention is concerned with such a disc harrow wherein crank arm movement is effected under the control of an hydraulic piston and cylinder assembly.
Tandem disc harrows of the general character outlined above and which employ front and rear pairs of disc gangs which are angularly adjustable to vary the included angle between adjacent gangs and thus vary the cultivation pattern are generally known. The purpose of adjusting the included angle is to vary the cultivation pattern, as well as to vary the width of the individual furrows created by the disc blades.
One currently employed method of varying the included angle between adjacent disc gangs embodies the use of gang beams which are interconnected in end-to-end fashion by connector plates at the apex of the included angle and which have their intermediate portions slidingly confined in the outer regions of the frame structure so that when a particular connector plate is moved in one longitudinal direction along the axis of the harrow, the included angle will be varied either to increase or decrease such angle, depending upon whether the front pair of disc gangs or the rear pair of disc gangs are concerned, and upon whether the connector plates are shifted forwardly or rearwardly. It is to this particular type of disc harrow and method varying the included angle between adjacent gang beams that the invention specifically relates.
Heretofore it has been customary to shift the connector plates at the juncture region between adjacent gang beams manually by the use of adjusting screw or worm drive mechanisms, such mechanisms possessing at least one disadvantage that considerable manual strength is required to actuate the same. Moreover, the provision of an extraneous hydraulic cylinder for the sole purpose of gang angling is relatively costly and requires an additional hydraulic circuit which often is not available.
The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and use of present day tandem disc harrows having facilities for varying the included angle between adjacent disc gangs and, toward this end, the invention contemplates the provision of a novel arrangement whereby the piston and cylinder assembly which is utilized for swinging the bell crank lever arrangement including the aforementioned pivot shaft, trailing wheel axle arms and crank arms, is also used in a selective manner to shift the connector plates of either the front or rear pair of disc gangs, each to the exclusion of the other, and in either a forward or a rearward direction, to thereby initiate either an increase or a decrease in the included angle of the associated pair of disc gangs. Moreover, the invention further embodies means whereby extremely small measured increments of beam angle adjustment may be effected as desired.
As will become more readily apparent when the nature of the invention is better understood, operator-control of the hydraulic cylinder is effected so that only that portion of the stroke of the cylinder plunger which takes place during raising or lowering of the frame structure after the disc blades have left the ground, or before they enter the ground, is used for connector plate shifting operations. The operator is thus able to measure small increments of angle change and apply them to the disc gangs by observing the motion of the disc blades from the time they leave the ground until the time they are fully raised, or vice versa.
The provision of a disc harrow which embodies such facilitates for varying the included angle between adjacent disc gangs constitutes the principal object of the present invention. Numerous other objects and advantages of the invention, not at this time set forth, will become readily apparent as the following description ensues. In such description and in the appended claims, the term "angling" will be employed to indicate connector plate shifting operations which result in decreasing the included angle between adjacent disc gangs, while the term "deangling" will be employed to indicate connector plate shifting operations which result in increasing such included angle or, in other words, straightening out the adjacent disc gangs toward positions of end-to-end alignment.